(1) Field of the Invention
The present invention generally relates to the field of electronic circuits. More specifically, the present invention relates to de-coupling circuits.
(2) Background Information
De-coupling capacitors are known in the art. Such capacitors may be used for de-coupling high-frequency noise voltages from a load circuit that may receive current from a power source. The noise is typically caused by the load current demand as well as the current source capability of the power supply circuit.
De-coupling of higher voltages may raise particular problems in the case where it is performed on-die by way of devices designed for a low-voltage process. Higher voltages may not be directly applied to on-die devices in a low voltage process because, as the applied voltage is increased, the devices to which the voltage is applied start degrading. In the case where the on-die de-coupling device is a transistor, the respective transistor may be degraded when operated beyond a prescribed range, i.e. when a higher voltage is applied thereto. In a particular instance, the behavior of a transistor in a Complementary Metal Oxide Semiconductor (CMOS) process depends upon the electric field to which the channel of the transistor may be subjected when a certain voltage is applied at the gate of the transistor. If a device such as a transistor is designed for a 3.3 volts process, and one needs to de-couple 4.6 volts, the gate oxide of the transistor operated at 4.6 volts may degrade over time, thus changing the characteristics of the device and consequently influencing the functionality of the device.
Accordingly, it is desirable to provide a reliable on-die de-coupling circuit using devices in a low-voltage process that in combination are able to handle higher voltages. It is desirable that the higher voltages applied to such de-coupling circuits do not cause a degradation of the on-die devices. It is also desirable that the de-coupling circuit consumes very little power.